A flow diverter for implantation into a patient's vessel includes a distal annular support element and a proximal annular support element, the proximal and distal support elements supporting a longitudinally twisted diverter element. The flow diverter is designed to be disposed within a vessel and to impart a rotational or twisting motion to the flow of blood passing therethrough, thereby to reduce the pressure of blood at the center of the vessel. Such flow diversion can reduce the pressure of blood impinging upon an aneurysm at a bifurcation downstream of the vessel. The device can be particularly useful for the treatment of aneurysms occurring at the bifurcation between the basilar artery and the posterior cerebral arteries.
